There has been some recent discussion that sugests that even for racing
triumphs best results are achieved with near stock needle profiles.
The stock needle listed for the stromberg carburated 1500 is (B5CH) in a
.100 jet. I can't find profiles for them in my Haynes stromberg book. When
I measure them they seem much richer than the stock SU needles (ABT) in a
090 jet, with a much steeper slope.
If I look at the orifice around the needles at a half inch (4 steps) the
B5CH is 0.0015, while the ABT is 0.0012 , reasonable similar . However at
1.25 inches (10 steps) the B5CH is 0.004 , while the ABT is 0.00239 . The
BG needle for the SU gives similar orifices to the B5CH stromberg needle.
The engine is currently configured as a 1300 and I would like to run twin
1.5 inch SU's. Runing with a single 1.5 inch strombergh it seems to run out
of torque above 6500 RPM using a needle that has orifices about twice that
of the B5CH. The cam has delived torque to 7500 in the past with twin SU's.
Sugestions?
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